Plasma chambers commonly are used to perform processes for fabricating electronic devices such as semiconductors, displays and solar cells. Such plasma fabrication processes include chemical vapor deposition of semiconductor, conductor or dielectric layers on the surface of a workpiece or etching of selected portions of such layers on the workpiece surface.
It is important for a plasma fabrication process to be performed with high spatial uniformity over the surface of the workpiece. For example, a deposition process should be performed so that the deposited material has uniform thickness and quality at all positions on the surface of the workpiece. Likewise, an etch process should etch material at a uniform rate at all such positions.
RF power can be capacitively coupled to plasma within a plasma chamber by coupling a source of RF power to an electrode positioned within, or adjacent to, the plasma chamber. In designs in which the RF power is coupled to a single point on the electrode, the plasma density, and hence the plasma fabrication process being performed on the workpiece, will suffer spatial non-uniformity if any dimension of the electrode is greater than approximately one-quarter wavelength of the RF power. Therefore, a need exists for improving such spatial uniformity.